Vehicle headlamps require horizontal and vertical adjustment to meet U.S. government legal aiming regulations. Headlamps frequently use angled gear drive adjusters for aiming.
Aiming is generally done with a simple tool or wrench by turning a screw or other similar device located behind the headlamp. Access to this area is important for without sufficient space to hand access, one cannot reach the adjuster in order to aim the headlamp. Right angle gear drives solve this problem as they need no rear access for adjustment. The drive shaft from the gear drive extends to the top of the headlamp for one to turn, which in turn moves the adjusting screw. The movement of the adjusting screw aims the headlamp.
The above-noted gear drives generally consist of two helical gears that are held in an engaged position in a housing. Some of these housings have sonic welded caps that permit loading of the gears and internal bushings.
The problem with previous gear drive adjusters is that their assembly involves a number of operations. The housing is designed to use several caps as covers over the pockets that contain the gears. The pockets are sealed when the caps are sonic welded to the housing, which can put the gears in a bind (if too tight) or result in a loose gear, which creates headlamp flutter, if improperly mounted to the housing.